Rotors for axial flow compressors or turbines



Jan. 20, 1959 F. 3. l. MARCHANT ETAL 2,869,320

ROTORS FOR AXIAL FLOW goMPREssoRs 0R TURBINES s Sheets-Sheet 1 FiledApril 12, 1952 Jan. 20, 1959 F. c. MARCHANT ETAL 2,369,320

ROTORS FOR AXIAL FLOW COMPRESSORS OR TURBINES I Filed April 12, 1952 3Sheets-Shet 2- 1 L I U I I I 26 12g 2% J 5": \,2% g E 5 2i 51 I 50 J3 vf a? w my? 53 llV/E/WWIS F6. 1. MAHCH/I/VT W. J MORLEY 5* E. BRIGGSUnited States Patent ROTORS FOR AXIAL FLOW COMPRESSORS 0R TURBINESFrancis Charles Ivor Marcllant, William James Morley, and Ernest Briggs,Bristol, England, assignors, by mesne assignments, to BristolAero=Engines Limited, Bristol, England, a British company AppiicationApril 12, 1952, Serial No. 281,958 Claims priority, application GreatBritain April 18, 1951 Claims. (Cl. 253-69) This invention relates torotors for rotary power conversion machines such as axial flowcompressors or turbines which rotors are of the kind comprising at leastthree blade-carrying discs joined at or near their rims to form a drumstructure.

A principal object of the invention is to provide such a structure whichwhile being light in weight and readily assembled and dismantled shallbe stiff against lateral defiections so a to provide a high criticalwhirling speed.

Another object of'the invention is to provide such a structure in which,while maintaining a minimum overall length of the rotor and itssupporting bearings, the end blade-carrying discs are substantiallyrelieved of bending stresses associated with lateral deflection.

According to the invention, in a rotor of the kind described, an endblade-carrying disc has a frusto-conical disc attached at each side at acommon intermediate radius one being convergent and carrying at its endof minimum diameter a stub shaft, and the other being divergent andforming part of another of the blade-carrying discs or being attached toanother such disc at or near its The invention also includes a rotor ofthe kind described in which the disc carrying the lowest pressureblading is flat and has a frusto-conical disc attached at each side at acommon intermediate radius, one being convergent and carrying at its endof minimum diameter a stub shaft, and the other being divergent andattached at its end of maximum diameter to the next adjacentblade-carrying disc at or, near its rim. t

In another arrangement according to the invention an end blade-carryingdisc has a central flat portion and an outer fr'usto-conical portiondiverging axially and radially away from the transverse central plane ofthe rotor, a convergent frusto-conical disc carrying at its end ofminimum diameter a stub shaft, being attached at its end of maximumdiameter at the margin of the central fiat portion on one side and onthe other side the next or next but one blade-carrying disc being ofoppositely dished planoconical form and attached directly or with aninterposed disc at the margin of said central flat portion.

All the blade-carrying discs may be secured together at or near theirrims with interposed spacing members by bolts extending from end to endof the drum structure assembly, or by bolts which are individual to the'bladecarrying discs.

Figure 1 illustrates an axial flow compressor having five stages (l-V)and intended for use as the low pressure compressor of a jet propulsioncompound gas turbine,

Figure 2 illustrates an axial fiow compressor having seven stages(l-VII) intended to follow the compressor illustrated in Figure 1 as ahigh pressure compressor,

Figure 3 illustrates an axial flow low pressure compressor having sixstages (IVI), the compressor being of the constant root diameter type,and

Figure 4 illustrates an axial flow highpressure compressor having eightstages (I-VIII), the compressor being' of the constant root diametertype." I

The compressor illustrated in Figure l is of the type having blades 5 ofconstant mean radius x and a ratio of hub diameter to tip diameter atthe first row of moving blades (a/ b) of about 0.45. The blades 5 aremounted around the rims of five discs 6, 7, 8a, 8b all of which aresolid, i. e. have no central holes. The first three discs 6, 7 are fiat,that is to say they are symmetrical on each side of a fiat centraltransverse plane, while the last two discs 8a and 8b at the highpressure end are dished toward one another and comprise central flatportions 9 in abutting relation and outer frusto-conical parts orportions 10 diverging from one another. Discs 6 and 8b constitute theend blade-carrying discs. At their rims the discs are spaced from oneanother by members 11 de fining the inner conical surface of the annularair passage 12 and are connected to the said spacing members by rows ofbolts 13 individual to each disc so as to form a frusto-conical drumstructure. At the high pressure end of the drum structure a shortconvergent frusto-conical disc 14 is bolted to the central flat portionof the end disc by bolts 15 which also pass through the fiat portion 9of the discs so that these three parts are firmly connected" At the lowpressure end of the rotor a similar short frusto-conical disc 19carrying a stub shaft 51 at its end of minimum diameter is bolted to theflat first stage disc 6 by a ring of bolts 20 arranged about midwaybetween its centre and rim. Disc 6 is advantageously made fiat sincethis is the best form for taking the centrifugal loads from the blading,which are highest for this stage, but it has the disadvantage with thearrangement as so far described that forces associated with lateraldefiection of the rotor tend to bend the disc, against which form ofdistortion it is relatively weak.

the conical disc 19, and therefore its projection, a frustoconical discor stiffening member 21 is attached to disc 6 by the bolts 29 andextends within the drum structure divergently to the rim of the secondstage disc 7, where its end of maximum diameter is sandwiched betweenthe rim and its spacing member 11.

Considering the rotor construction in'axial section, the vfrusto-conical disc 19, frusto-conical stifiening member 21, spacingmembers 11 between the discs 7, 8a of stages 11, III and IV, disc 8a ofstage IV and frusto-conical disc 14 form a strength drum of generallypeg top form from which the discs 6 and 8b project and are stabilised bythe first and last spacing members 11.

Referringto Figure 2, in this case the blade-carrying discs 25a, 25b, 26and 27a, 27b are all provided with central holes for the passage of theshaft 17 driving the low pressure compressor.

The high pressure compressor has a constant tip diameter, so that therotor drum has a conical outer surface 'as in the construction of Figure1, in this case however the hub-tip ratio is very much smaller, beingabout 0.69, and this has permitted the first and second stage discs 25a,25b to be dished towards one another to form a construction as describedfor the high pressure end of the construction of Figure l, afrusto-conical disc 31 carrying a stub shaft 53 being bolted to thediscs 25a, 25b. The high pressure end is also constructed in a similarmanner but has an additional frusto-conical disc 28 carry ing at its endof maximum diameter part of a labyrinth seal 29. The additional disc 28has its end of minimum Patented Jan. 20, 1959 To overcome this objectionwithout increasing the maximum diameter and taper of diameter sandwichedbetweenthe disc 27b and the frustoconical disc 38 which carries a stubshaft 54. The two stub shafts 53, 54 also retain between them a tubularmember 32 passing through the central holes of the discs. The discs 26of stages Eli and V bear on the outside of this tubular member, as at33, for steadying purposes, the remaining discs being provided withclearance holes.

Referring to Figure 3, in the compressor rotor illustrated the first rowof moving blades has a hub tip ratio of about 0.6, the first and secondand the fifth and sixth blade-carrying discs 35a, 35b, 36a, 36brespectively (i. e. at the ends of the rotor) are dished towards oneanother and provided with frusto-conical discs 39 carrying stub shaftsas described above for the high pressure end in the construction ofFigure 1. At their rims all the bladecarrying discs are bolted togetherwith interposed spacing members 37 defining the inner cylindricalsurface of the air passage between the blades by a ring of bolts 38extending from end to end of the rotor. To ensure correct re-assemblyafter dismantling, each of the bolted joints is preferably provided witha locating peg or dowel (not shown) and similar provision may be made inthe other constructions described.

In the construction shown in Figure 4 the compressor rotor has a hub-tipratio at the first row of moving blades of about 0.75 and is constructedas described with reference to Figure 3 except that at the low pressureend, instead of the first and second discs being dished towards oneanother, the second disc 46 is fiat and clamped at an intermediateradius between the first and third discs 41a, 41b, which are dishedtowards the disc 40, a frustoconical disc 42 carrying a stub shaft 56 atits end of minimum diameter being also attached at the same clampingradius. The other discs in this construction all have central holes forthe passage of a shaft for driving an adjacent low pressure compressor,the discs being suitably increased in thickness around the holes toprovide the necessary reinforcement as described with reference toFigure 2. All the discs except the second extend inwardly to a tube heldbetween the stub shafts, the second projecting only a short distanceinwardly of the clamping radius and being provided around the centralhole with a thickened rim 43 spigotting into recesses 44 in the disc41a, 41b so that these latter provide an anchorage for the inner rim. Attheir outer rims the discs are held together with interposed spacingmembers 45 by bolts (at 46) extending from end to end of the rotor as inthe third construction.

The several constructions described with reference to the accompanyingdrawings are given by way of example only.

The invention is also applicable to rotor constructions in which theblades are held between adjacent discs instead of being mounted aroundthe disc rims. In such constructions the blades take the place of thespacing members previously referred to, while the rims of the discs formthe inner surface of the annular air passage between the blade rows.

Although the invention has been particularly described as applied tocompressors it will be clear that the same principles can apply in thecase of multi-stage axial flow turbines.

We claim:

1. In a lightweight rotor for an axial flow rotary power conversionmachine said rotor comprising at least two end blade-carrying discs, anintermediate blade-carrying disc, and means joining said discs togetherand connected thereto adjacent their rims to form a rigid drumstructure: a first frusto-conical disc bolted at an intermediate radiusto the side of one of said end blade-carrying discs forming an end faceof said drum structure, said frustoconical disc being of a lessermaximum diameter than said end blade-carrying disc and being carried bysaid end blade-carrying disc so as to be concentric therewith'andconvergent away therefrom, a stub shaft for 4. said rotor on said firstfrusto-conical disc at its end of minimum diameter; a blade carryingdisc having at least a frusto-conical part bolted to said one endbladecarrying disc at said intermediate radius on the side thereofremote from said first frusto-conical disc so as to be concentric withsaid one end blade-carrying disc, said frusto-conical part beingdivergent away from said one end blade carrying disc; and boltsattaching said rusto-conical part at its end of maximum diameter to theouter periphery of an adjacent part of said drum structure.

2. A rotor as claimed in claim 1 wherein said one of said endblade-carrying discs has a central flat portion and an outerfrusto-conical portion diverging axially and radially away from thetransverse central plane of the rotor, and said first frusto-conicaldisc is bolted to said one end blade-carrying disc at the margin of saidcentral fiat portion, and said blade-carrying disc having thefrusto-conical part is next adjacent to said one end bladecarrying discand said frusto-conical part is bolted to said one of said endblade-carrying discs at the margin of said central flat portion.

3. A rotor as claimed in claim 1 wherein said means to join saidblade-carrying discs together adjacent their rims comprises a pluralityof bolts and interposed spacing members, between each adjacent pair ofdiscs.

4. In a lightweight'rotor for an axial flow rotary power conversionmachine said rotor comprising at least two end blade-carrying discs, anintermediate blade carrying disc, and means joining said discs togetherand connected thereto adjacent their rims to form a rigid drumstructure: a first frusto-conical disc bolted at an intermediate radiusto the side of one of said end blade-carrying discs forming an end faceof said drum structure, which end blade-carrying disc is fiat, saidfrusto-conical disc being of a lesser maximum diameter than said one endbladecarrying disc and being carried by said one end bladecarrying discso as to be concentric therewith and convergent away therefrom, a stubshaft for said rotor on said first frusto-conical disc; and a secondfrusto-conical disc bolted to said one end blade carrying disc at saidintermediate radius on the side thereof remote from said firstfrusto-conical disc so as to be concentric with said one endblade-carrying disc, said second frusto-conical disc being divergentaway from said one end blade-carrying disc and being bolted to saidintermediate bladecarrying disc.

5. In a lightweight rotor for an axial flow rotary power conversionmachine said rotor comprising at least two end blade-carrying discs, anintermediate blade-carrying disc, and means joining said discs togetherand connected thereto adjacent their rims to form a rigid drumstructure: a first frusto-conical disc bolted at an intermediate radiusto the side of one of said end blade-carrying discs forming an end faceof said drum structure, said frustoconical disc being of a lessermaximum diameter than said one end blade-carrying disc and being carriedby said one end blade-carrying disc so as to be concentric therewith andconvergent away therefrom, a stub shaft for said rotor on said firstfrusto-c'onical disc; and a second frusto-conical disc bolted to saidone end blade-carrying disc at said intermediate radius on the sidethereof remote from said first frusto-conical disc so as to beconcentric with said one end blade-carrying disc, said secondfrusto-conical disc being divergent away from said one endblade-carrying disc and being bolted at its end of maximum diameter tosaid intermediate blade-carrying disc. I

6. A rotor as claimed in claim 1, wherein said one of said end bladecarrying discs is an unpcrforated disc, and said blade carrying dischaving at least a frusto-conical part is an unperforated disc, thefrusto-conical part forming an outer peripheral portion of the disc.

7. A rotor as claimed in claim 2, wherein the cone angle of the outerfrusto conical portion of said one end blade carrying disc issubstantially equal to the cone angle of said frusto-conical part.

8. A rotor as claimed in claim 2, wherein said central flat portion ofsaid one of said end blade carrying discs is unperforated, and said nextadjacent blade carrying disc has a central unperforated flat portion.

9. A rotor as claimed in claim 2, further comprising spacing meansbetween said frusto-conical part and said one of said end blade carryingdiscs, the frusto-conical part being bolted to said one of said endblade carrying discs through said spacing means.

10. In a lightweight rotor for an axial flow rotary power conversionmachine, said rotor comprising a plurality of blade carrying discsincluding at least two endblade carrying discs and means joining saiddiscs together and connected thereto adjacent their rims to form a rigiddrum structure; a first frusto-conical disc bolted at an intermediateradius to the side of the end blade carrying disc at the low pressureend of the rotor which forms an end face of said drum structure, saidfirst frusto-conical disc being of a lesser maximum diameter than saidlow pressure end blade carrying disc, and being carried by said lowpressure end blade-carrying disc so as to be concentric therewith andconvergent away therefrom; a first stub shaft for said rotor on saidfirst frusto-conical disc at its end of minimum diameter; a secondfrusto-conical disc bolted to said low pressure end blade carrying discat said intermediate radius on the side thereof remote from said firstfrusto-conical disc so as to be concentric with said low pressure endblade carrying disc, said second frusto-conical disc being divergentaway from said low pressure end blade carrying disc and being bolted atits end of maximum diameter to said drum structure at the outerperiphery of the drum structure; a third frusto conical disc bolted atan intermediate radius to the side of the end blade carrying disc at thehigh pressure end of the rotor which forms the other end face of saiddrum structure, said third frusto-conical disc being of lesser maximumdiameter than said high pressure end bladecarrying disc and beingcarried by said high pressure end blade-carrying disc so as to beconcentric therewith and convergent away therefrom; a second stub shaftfor said rotor on said third frusto-conical disc at its end of minimumdiameter; a blade carrying disc having at least a frusto-conical partbolted to said high pressure end blade carrying disc at saidintermediate radius of the high pressure end blade carrying disc on theside thereof remote from said third frusto-conical disc so as to beconcentric with said high pressure end blade carrying disc, saidfrusto-conical part being divergent away from said high pressure endblade carrying disc; and bolts attaching said frusto-conical part at itsend of maximum diameter to the outer periphery of said drum structure.

References Cited in the file of this patent UNITED STATES PATENTS770,207 Wilkinson Sept. 13, 1904 1,030,153 Barbezat June 18, 19122,213,940 Jendrassik Sept. 3, 1940 2,445,661 Constant et a1. July 20,1948 2,579,745 Lombard Dec. 25, 1951 2,662,685 Blane Dec. 15, 1953FOREIGN PATENTS 223,615 Switzerland Dec. 16, 1942 543,985 Great BritainMar. 23, 1942

